The instant invention relates to a drive arrangement of an open-end spinning machine. The open-end spinning machine shall be referred to hereinafter as OE spinning machine for short.
The instant invention relates here to a drive arrangement capable of serving all the spinning stations of the OE spinning machine or one group of spinning stations of this spinning machine with a plurality of spinning stations. Generally such OE spinning machines have a row of spinning stations on either longitudinal side of the machine and it is then possible to either provide for one and the same drive arrangement to drive both rows of spinning stations or to provide either row of spinning stations or each one of some other plurality of groups of spinning stations with its own drive arrangement. The OE spinning machine can be a rotor spinning machine as well as a friction spinning machine. In such OE spinning machines fiber slivers are conveyed by feed rollers to opener rollers which open them into individual fibers and these are conveyed from said opener rollers to fiber collection and twist-producing elements, and in case of a rotor spinning machine to spinning rotors, and in case of a friction spinning machine into a groove formed by two rollers driven in the same direction in which they twisted into a sliver. The fibers collected in the spinning rotor or against the friction rollers are twisted into yarns and each yarn is continuously drawn off by a pair of draw-off rollers and is wound up into a cross-wound bobbin which is driven at its circumference by a winding roller.
The degree of draft in such an OE spinning machine is determined by the relationship between the draw-off speed at which the yarn in question is conveyed by the pair of draw-off rollers and the speed at which the feed roller conveys the fiber sliver to be opened into individual slivers to the opener rollers.
It is desirable to keep the degree of draft constant in normal operation. Until now the procedure for this in conventional OE spinning machine consisted in driving the elements of its spinning stations to be driven, with the exception of the opener rollers, with a common main motor via mechanical gears, among these also toothed-wheel change gears. The construction costs for this are however very high. Also, each change of the degree of draft and of the yarn number to be produced requires a considerable amount of work time and also requires interchangeable gears for toothed-wheel change gears. Each of the opener rollers was driven by a separate motor on either side of the machine, each via a continuously adjustable mechanical gear arrangement.
Depending on the number of electrical networks and on their manner of operation, brief power interruptions, in the order of milliseconds up to a maximum of 2 seconds as based on European standards, are possible. To bridge this outage time an emergency current supply system was designed for spinning machines in the past. Outside of Europe however, and despite constantly improvising automation and precision of spinning machines, outage times exceeding approximately five times the familiar duration of brief network outages must be expected, and it therefore becomes necessary to overcome this extreme duration of brief network outage. In order to compensate in general for the effect of this interference with the technical operation of the spinning machine, the availability of electric energy for operating current as well as for control current must be ensured for longer periods of time (five times longer) than with network outages in the past, lastly normally up to two seconds, i.e. electrical energy must be made available for the spinning machine in particular for the extreme duration of brief network outage. The concept of brief network outage must be broken down in time since qualitatively different problems occur with the extreme duration of brief network outage (up to approximately 10 seconds) than in the time range of milliseconds up to 2 seconds, i.e. because a considerably higher, immediately available energy quantum must be made available for the drive arrangements, for example.
To bridge brief network outages of up to max. 2 seconds, centrifugal masses representing a defined kinetic energy were provided in the past at the shaft of the spinning machine, representing an equivalent of electric energy reserves when a switch-over from motor operation to generator operations is effected in case of electric network outage.
An increase of these centrifugal masses in conventional spinning machines has limits since these masses must be accelerated constantly, and this has unfavorable consequences for the acceleration capability of a supply shaft. Also, these centrifugal masses cannot be varied on the shaft in function of different kinetic energy requirements.
The variety of circuitry for controls and regulation on drives in general, such as for example the formation of the impulse pattern to trigger the output semi-conductor or to signal malfunctions are explained with the utilization of microprocessors, indicating that the utilization of three-phase-current machines requires special regulation, but without any indication of a solution for the special case of brief network outages of extreme duration.
The known solutions (as shown in Publication Meier, Urs.: Mehrmotorenantriebe. in: STZ, No. 11, Jun. 1, 1988, pages 8-10 or DE 25 21 940 C2, DE 26 43 625 A1, DE 27 53 924 A1) give no indications on the basis of which the problem tackled by the instant invention can be solved. The solution given by DE 33 47 113 C2 is based on managing the network outage during piecing with the aim of stopping the machine in a controlled manner. However this problem and solution represent considerable limitations.
Neither does DE 36 41 569 C1 go beyond this. DE 36 41 569 C1 continues to manage an optimal spinning program, with greater regulating possibilities than in DE 33 47 113 C2. Neither solution however can guarantee the bridging of the brief network outage while the spinning program continues to be carried out in technical operation.
It is an objective of the instant invention to simplify the drive arrangement of such an open-end spinning machine or, if it requires several drive arrangements for an equal number of spinning station groups, each with a plurality of spinning stations, for each such group of spinning stations, whereby the brief network outage can be managed more completely in time without technological limitations and whereby the change-over to different yarn numbers to be produced and to different degrees of yarn twist is considerably simplified.